update-namecheap

#!/usr/bin/env bash
################################################################################
# update-namecheap - simple script for updating Namecheap's dynamic DNS service.
#
# Dependencies: curl (should be found almost everywhere)
#
# Version 1
# Matthew Malensek <matt@malensek.net>
################################################################################

unset username password ip
update_url='dynamicdns.park-your-domain.com/update'

print_usage() {
cat <<EOM
Usage: $(basename ${0}) -u username -p password [-i ip_addr] host

Updates the Namecheap dynamic DNS for a given host.  Dynamic DNS must be turned
on in the Namecheap settings.  Options:

    * -u Namecheap dynamic DNS username (domain name) e.g., somewhere.org
    * -p dynamic DNS password (long alphanumeric string generated by Namecheap)
    * -i ip address (optional).  If not provided, the requesting IP is used.

    host - the hostname to update, for instance when updating
    site.somewhere.org, host will be 'site.'  To update the base hostname,
    provide '@'.  You may also have a '*' record set up that can be changed.

    Examples:
        $(basename ${0}) -u somewhere.org -p abc123etcetc mysite
        $(basename ${0}) -u somewhere.org -p abc123etcetc @
        $(basename ${0}) -u somewhere.org -p abc123etcetc -i 127.0.0.1 othersite
EOM
}

read_xml () {
    local IFS=\>
    read -d \< tag value
}

while getopts "u:p:i:" flag; do
    case ${flag} in
        u) username=${OPTARG} ;;
        p) password=${OPTARG} ;;
        i) ip=${OPTARG} ;;
        ?) print_usage; exit 1 ;;
    esac
done

if [[ -z "${username}" || -z "${password}" ]]; then
    echo "A username (-u) and password (-p) must be specified."
    echo
    print_usage
    exit 1
fi

shift $(($OPTIND - 1))

host=${1}
if [[ -z ${1} ]]; then
    echo "No host specified to update!"
    echo
    print_usage
    exit 1
fi

url="https://${update_url}?host=${host}&domain=${username}&password=${password}"
if [[ -n "${ip}" ]]; then
    url="${url}&ip=${ip}"
fi

response=$(curl "${url}" 2> /dev/null)

errors=0
while read_xml; do
    if [[ "${tag}" == "ErrCount" ]]; then
        errors=${value}
        if [[ ${errors} -eq 0 ]]; then
            # There were no errors; we are done.
            exit 0
        fi
        continue
    fi

    if [[ ${errors} -gt 0 && "${tag}" == "Err"* ]]; then
        echo 1>&2 "ERROR: ${value}"
    fi
done <<< "${response}"

# If execution reaches this point, errors were listed. Set a failed exit code.
exit 1